Knife sharpener



FIG. 1 is a front isometric view of a knife sharpener, embodying the new design.

FIG. 2 is a front view of the design of FIG. 1.

FIG. 3 is a rear view of the design of FIG. 1.

FIG. 4 is a top plan view of the design of FIG. 1.

FIG. 5 is a bottom plan view of the design of FIG. 1.

FIG. 6 is a right side view of the design of FIG. 1; and,

FIG. 7 is a left side view of the design of FIG. 1. 

CLAIM The ornamental design for a knife sharpener, as shown and described. 